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Voltage-mode FDCCII-based universal filters
Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323 www.elsevier.de/aeue
LETTER
Voltage-mode FDCCII-based universal filters Hua-Pin Chen∗ Department of Electronic Engineering, De-Lin Institute of Technology, Taiwan, ROC Received 26 July 2006; accepted 4 May 2007
Abstract Three new voltage-mode universal biquadratic filters configuration are proposed. The first proposed high-input impedance universal filter with single input and five outputs, which can simultaneously realize voltage-mode lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filter responses employing all grounded passive components. The second proposed high-input impedance universal filter with three input and single output, which also can realize all the standard filter functions without requiring any inverting input voltage signal. The third proposed universal filter with three inputs and five outputs, which can be used as either a three-input single-output or a two-input five-output universal filter. Moreover, each of the proposed circuits still enjoys (i) the employment of only grounded capacitors, and (ii) no requirement with the component choice conditions to realize specific filtering functions. 䉷 2007 Published by Elsevier GmbH Keywords: Universal filter; Voltage-mode circuits; Filters; Current conveyors
1. Introduction Active filters with high-input impedance are of great interest because it can be easily cascaded to synthesize highorder filters [1,2,7,16,18]. Both the use of grounded resistors and capacitors are more beneficial from the point of view of integrated circuit implementation [3]. In 2000, a new active element called the fully differential current conveyor (FDCCII) was proposed [4] to improve the dynamic range in mixed-mode applications where fully differential signal processing was required. Many voltage-mode multifunction filters using current conveyors were proposed [5–10]. But those cannot realize five filtering responses simultaneously. In 2005 and 2006, Horng et al. proposed six universal biquad filters with a single input and five outputs using two–four current conveyors, two grounded capacitors and four–seven
∗ Corresponding author. Tel.: +886 2 22733567x388.
E-mail address: [email protected]. 1434-8411/$ - see front matter 䉷 2007 Published by Elsevier GmbH doi:10.1016/j.aeue.2007.05.002
resistors [11,12]. However, these proposed configurations used much more passive components and required a matching condition to realize allpass (AP) filter response and also cannot enjoy the high-input impedance at the input terminal. In this paper, the first proposed circuit utilized the voltage addition and subtraction characteristics of an FDCCII to realize voltage-mode universal biquad filter with signal input and five outputs using two grounded capacitors and two grounded resistors. The proposed circuit offers three more advantages compared with the recent works [11,12]: (i) it has high-input impedance, (ii) it does not require component matching conditions, and (iii) it employs minimum passive components. Some universal voltage-mode biquads with multiple inputs and one or two outputs were proposed [13–18]. In 2001 and 2004, Horng [16,18] proposed two high-input impedance voltage-mode universal filters with three inputs and one or two outputs employing three plus-type second-generation current conveyors, two capacitors and two resistors. However, those still needed an inverting-type
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
voltage input signal to realize the AP filter response and even more required a matching condition to realize notch and AP filter responses. In this paper, the second proposed universal voltage-mode filter with three inputs and one output employing two FDCCIIs, two grounded capacitors and two grounded resistors. The proposed circuit offers the following features: (i) the employment of only grounded capacitors and resistors, (ii) high-input impedance, (iii) no need to employ inverting type input signals, and (iv) no requirement with the component choice conditions to realize specific filtering functions. As can be seen, none of the filters [13–18] is capable of achieving the four performance parameters simultaneously. In 2003, Chang et al. [19] proposed a voltage-mode multifunction filter with single input and four outputs using single FDCCII and four passive components. But only three standard filter functions at most can be simultaneously obtained in the circuit design. In 2005, Chang and Chen [20] proposed another voltage-mode universal filter with threeinputs and single output using a single FDCCII, two capacitors and three resistors. But one of capacitor could not be grounded and still needed inverting-type voltage input signal to realize the allpass filter response. In this paper, the third proposed voltage-mode universal filter with three inputs and five outputs using a single FDCCII, two grounded capacitors and two resistors which is unlike the recent works by Chang et al. [19,20].
2. Circuit description Using standard notation, the input–output relationship of an FDCCII is characterized by IY 1 = IY 2 = IY 3 = IY 4 = 0, VX+ = VY 1 − VY 2 + VY 3 , VX− = VY 2 − VY 1 + VY 4 , IZ+ = IX+ , and IZ− = IX− [4]. The first proposed voltage-mode universal biquad with high input impedance is shown in Fig. 1. Circuit analysis yields the following five filter voltage transfer functions: VBP Vo1 sC 2 G1 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2 VLP Vo2 −G1 G2 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
321
Fig. 2. The second proposed universal filter.
VHP Vo3 s 2 C 1 C2 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
(3)
VBS Vo4 −(s 2 C1 C2 + G1 G2 ) = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
(4)
VAP Vo5 −(s 2 C1 C2 − sC 2 G1 + G1 G2 ) = = . Vi Vi s 2 C1 C2 + sC 2 G1 + G1 G2
(5)
The resonance angular frequency o and quality factor Q are given by
(1)
o =
(2)
G1 G2 , C1 C 2
Q=
C1 G 2 . C2 G 1
(6)
The second proposed voltage-mode universal biquad with high input impedance is shown in Fig. 2. The output voltage can be expressed as Vo =
s 2 C1 C2 Vi1 − sC 2 G1 Vi2 + G1 G2 Vi3 . s 2 C1 C2 + sC 2 G1 + G1 G2
(7)
The resonance angular frequency o and quality factor Q are given by o = Fig. 1. The first proposed universal filter.
G1 G2 , C1 C 2
Q=
C1 G 2 . C2 G 1
(8)
322
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
Depending on the voltage status of Vi1 , Vi2 , and Vi3 in the numerator of Eq. (14), one of the following five filter functions is realized: (i) (ii) (iii) (iv) (v)
LP: Vi1 = Vi3 = 0, and Vi2 = Vi , BP: Vi1 = Vi2 = 0, and Vi3 = Vi , HP: Vi2 = Vi3 = 0, and Vi1 = Vi , BS: Vi3 = 0, and Vi1 = Vi2 = Vi , AP: Vi1 = Vi2 = −Vi3 = Vi .
The resonance angular frequency o and quality factor Q are given by G1 G2 C1 G 1 , Q= . (15) o = C1 C2 C2 G 2 Although an inverting voltage input signal is used for realizing the allpass signal. This disadvantage vanishes if we make the resistor R2 be grounded, the capacitor C2 be floating, and insert the voltage input signal Vi3 into the floating terminal of the capacitor C2 , then
Fig. 3. The third proposed universal filter.
Depending on the voltage status of Vi1 , Vi2 and Vi3 in the numerator of Eq. (7), one of the following five filter functions is realized: (i) (ii) (iii) (iv) (v)
LP: Vi1 = Vi2 = 0, and Vi3 = Vi , BP: Vi1 = Vi3 = 0, and Vi2 = Vi , HP: Vi2 = Vi3 = 0, and Vi1 = Vi , BS: Vi2 = 0, and Vi1 = Vi3 = Vi , AP: Vi1 = Vi2 = Vi3 = Vi .
Vo3 =
s 2 C1 C2 Vi1 − sC 2 G2 Vi3 + G1 G2 Vi2 . s 2 C1 C2 + sC 2 G2 + G1 G2
(16)
The AP signal can be obtained from the output terminal Vo3 provided Vi1 = Vi2 = Vi3 = Vi . Note that no inverting amplifiers are needed to construct an AP biquad.
3. Conclusion
The third proposed circuit can be used as either a threeinput single-output or a two-input five-output universal filter is shown in Fig. 3. Circuit analysis yields the following transfer functions: If Vi1 = Vi2 = Vi , and Vi3 = 0, then
Three new voltage-mode universal biquadratic filters are proposed. The first proposed circuit utilized the voltage addition and subtraction characteristics of an FDCCII, which could realize voltage-mode universal biquad filter with arithmetic operations. The second proposed circuit did not need to employ inverting type input signal to realize the five standard filter functions. Moreover, both two universal biquad filters still had the following four main advantages: use of all grounded capacitors and resistors, high-input impedance, no need of matching constraints and no need inverting-type voltage input signals. The third proposed circuit with minimum active and passive components and can be used as either a three-input single-output or a two-input five-output universal filter, which cannot be enjoyed by the previously reported works [5–20].
−G1 G2 Vo1 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(9)
Vo2 s 2 C1 C2 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(10)
Vo3 s 2 C1 C2 + G 1 G 2 = 2 , s C1 C2 + sC 2 G2 + G1 G2 Vi
(11)
Vo4 sC 2 G2 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(12)
Acknowledgement
Vo5 Vo3 − Vo4 s 2 C1 C2 − sC 2 G2 + G1 G2 = = 2 . Vi Vi s C1 C2 + sC 2 G2 + G1 G2
(13)
The author is thankful to the anonymous reviewers for useful suggestions on the earlier version of this paper that improved the paper quality.
On the other hand, the output terminal Vo3 transfer function can be expressed as Vo3 =
s 2 C1 C2 Vi1 + G1 G2 Vi2 + sC 2 G2 Vi3 . s 2 C1 C2 + sC 2 G2 + G1 G2
(14)
References [1] Liu SI, Tsao HW. The single CCII biquads with high-input impedance. IEEE Trans Circuit Syst 1991;38:456–61.
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
[2] Fabre A, Dayoub F, Duruisseau L, Lamoun M. High input impedance insensitive second-order filters implemented from current conveyors. IEEE Trans Circuits and Systems – I: Fundam Theory Appl 1994;41:918–21. [3] Chang CM, Al-Hashimi BM, Chen HP, Tu SH, Wan JA. Current mode single resistance controlled oscillators using only grounded passive components. Electron Lett 2002;38:1071–2. [4] El-Adawy AA, Soliman AM, Elwan HO. A novel fully differential current conveyor and applications for analog VLSI. IEEE Trans Circuits and Systems – II: Analog Digital Signal Process 2000;47:306–13. [5] Soliman AM. Kerwin–Huelsman–Newcomb circuit using current conveyors. Electron Lett 1994;30:2019–20. [6] Senani R, Singh VK. KHN-equivalent biquad using current conveyors. Electron Lett 1995;31:626–8. [7] Horng JW, Lay JR, Chang CW, Lee MH. High input impedance voltage-mode multifunction filters using plus-type CCII’s. Electron Lett 1997;33:472–3. [8] Chang CM. Multifunction biquadratic filters using current conveyors. IEEE Trans Circuits and System – II: Analog Digital Signal Process 1997;44:956–8. [9] Chang CM, Lee MJ. Voltage-mode multifunction filter with single input and three outputs using two compound current conveyors. IEEE Trans Circuits and Systems – I: Fundam Theory Appl 1999;46:1364–5. [10] Horng JW, Chiu WE, Wei HY. Voltage-mode highpass, bandpass and lowpass filters using two DDCCs. Int J Electron 2004;91:461–4. [11] Horng JW, Hou CL, Chang CM, Chung WY, Wei HY. Voltage-mode universal biquadratic filter with one input and five outputs using MOCCIIs. Comput Electr Eng 2005;31: 190–202. [12] Horng JW, Hou CL, Chang CM, Chung WY, Wei HY. Voltagemode universal biquadratic filters with one input and five outputs. Analog Integr Circuits and Signal Process 2006;47: 73–83. [13] Horng JW, Tsai CC, Lee MH. Novel universal voltage-mode biquad filter with three inputs and one output using only two current conveyors. Int J Electron 1996;80:543–6.
323
[14] Liu SI, Lee JL. Voltage-mode universal filters using two current conveyors. Int J Electron 1997;82:145–9. [15] Chang CM, Tu SH. Universal voltage-mode filter with four inputs and one output using two CCII + s. Int J Electron 1999;86:305–9. [16] Horng JW. High-input impedance voltage-mode universal biquadratic filter using three plus-type CCIIs. IEEE Trans Circuits and Systems – II: Analog Digital Signal Process 2001;48:996–7. [17] Chang CM, Chen HP. Universal capacitor-grounded voltagemode filter with three inputs and a single output. Int J Electron 2003;90:401–6. [18] Horng JW. High input impedance voltage-mode universal biquadratic filters with three inputs using three plus-type CCIIs. Int J Electron 2004;91:465–75. [19] Chang CM, Al-Hashimi BM, Wang CL, Hung CW. Single fully differential current conveyor biquad filters. IEE Proc Circuits Dev Syst 2003;150:394–8. [20] Chang CM, Chen HP. Single FDCCII-based tunable universal voltage-mode filter. Circuit Syst Signal Process 2005;24: 221–7. Hua-Pin Chen was born in Taipei, Taiwan, Republic of China, in 1966. He received the M.S. and Ph.D. degrees from Chung Yuan Christian University, Chung, Taiwan, in 2001 and 2005, respectively. Since August 2005, he is affiliated as Assistant Professor in the Department of Electronic Engineering at the De-Lin Institute of Technology, Taiwan. His teaching and research interests are in the areas of Circuits and Systems, Analog and Digital Electronics, Active Filter Design, and Current-Mode Signal Processing.
LETTER
Voltage-mode FDCCII-based universal filters Hua-Pin Chen∗ Department of Electronic Engineering, De-Lin Institute of Technology, Taiwan, ROC Received 26 July 2006; accepted 4 May 2007
Abstract Three new voltage-mode universal biquadratic filters configuration are proposed. The first proposed high-input impedance universal filter with single input and five outputs, which can simultaneously realize voltage-mode lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filter responses employing all grounded passive components. The second proposed high-input impedance universal filter with three input and single output, which also can realize all the standard filter functions without requiring any inverting input voltage signal. The third proposed universal filter with three inputs and five outputs, which can be used as either a three-input single-output or a two-input five-output universal filter. Moreover, each of the proposed circuits still enjoys (i) the employment of only grounded capacitors, and (ii) no requirement with the component choice conditions to realize specific filtering functions. 䉷 2007 Published by Elsevier GmbH Keywords: Universal filter; Voltage-mode circuits; Filters; Current conveyors
1. Introduction Active filters with high-input impedance are of great interest because it can be easily cascaded to synthesize highorder filters [1,2,7,16,18]. Both the use of grounded resistors and capacitors are more beneficial from the point of view of integrated circuit implementation [3]. In 2000, a new active element called the fully differential current conveyor (FDCCII) was proposed [4] to improve the dynamic range in mixed-mode applications where fully differential signal processing was required. Many voltage-mode multifunction filters using current conveyors were proposed [5–10]. But those cannot realize five filtering responses simultaneously. In 2005 and 2006, Horng et al. proposed six universal biquad filters with a single input and five outputs using two–four current conveyors, two grounded capacitors and four–seven
∗ Corresponding author. Tel.: +886 2 22733567x388.
E-mail address: [email protected]. 1434-8411/$ - see front matter 䉷 2007 Published by Elsevier GmbH doi:10.1016/j.aeue.2007.05.002
resistors [11,12]. However, these proposed configurations used much more passive components and required a matching condition to realize allpass (AP) filter response and also cannot enjoy the high-input impedance at the input terminal. In this paper, the first proposed circuit utilized the voltage addition and subtraction characteristics of an FDCCII to realize voltage-mode universal biquad filter with signal input and five outputs using two grounded capacitors and two grounded resistors. The proposed circuit offers three more advantages compared with the recent works [11,12]: (i) it has high-input impedance, (ii) it does not require component matching conditions, and (iii) it employs minimum passive components. Some universal voltage-mode biquads with multiple inputs and one or two outputs were proposed [13–18]. In 2001 and 2004, Horng [16,18] proposed two high-input impedance voltage-mode universal filters with three inputs and one or two outputs employing three plus-type second-generation current conveyors, two capacitors and two resistors. However, those still needed an inverting-type
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
voltage input signal to realize the AP filter response and even more required a matching condition to realize notch and AP filter responses. In this paper, the second proposed universal voltage-mode filter with three inputs and one output employing two FDCCIIs, two grounded capacitors and two grounded resistors. The proposed circuit offers the following features: (i) the employment of only grounded capacitors and resistors, (ii) high-input impedance, (iii) no need to employ inverting type input signals, and (iv) no requirement with the component choice conditions to realize specific filtering functions. As can be seen, none of the filters [13–18] is capable of achieving the four performance parameters simultaneously. In 2003, Chang et al. [19] proposed a voltage-mode multifunction filter with single input and four outputs using single FDCCII and four passive components. But only three standard filter functions at most can be simultaneously obtained in the circuit design. In 2005, Chang and Chen [20] proposed another voltage-mode universal filter with threeinputs and single output using a single FDCCII, two capacitors and three resistors. But one of capacitor could not be grounded and still needed inverting-type voltage input signal to realize the allpass filter response. In this paper, the third proposed voltage-mode universal filter with three inputs and five outputs using a single FDCCII, two grounded capacitors and two resistors which is unlike the recent works by Chang et al. [19,20].
2. Circuit description Using standard notation, the input–output relationship of an FDCCII is characterized by IY 1 = IY 2 = IY 3 = IY 4 = 0, VX+ = VY 1 − VY 2 + VY 3 , VX− = VY 2 − VY 1 + VY 4 , IZ+ = IX+ , and IZ− = IX− [4]. The first proposed voltage-mode universal biquad with high input impedance is shown in Fig. 1. Circuit analysis yields the following five filter voltage transfer functions: VBP Vo1 sC 2 G1 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2 VLP Vo2 −G1 G2 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
321
Fig. 2. The second proposed universal filter.
VHP Vo3 s 2 C 1 C2 = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
(3)
VBS Vo4 −(s 2 C1 C2 + G1 G2 ) = = 2 , Vi Vi s C1 C2 + sC 2 G1 + G1 G2
(4)
VAP Vo5 −(s 2 C1 C2 − sC 2 G1 + G1 G2 ) = = . Vi Vi s 2 C1 C2 + sC 2 G1 + G1 G2
(5)
The resonance angular frequency o and quality factor Q are given by
(1)
o =
(2)
G1 G2 , C1 C 2
Q=
C1 G 2 . C2 G 1
(6)
The second proposed voltage-mode universal biquad with high input impedance is shown in Fig. 2. The output voltage can be expressed as Vo =
s 2 C1 C2 Vi1 − sC 2 G1 Vi2 + G1 G2 Vi3 . s 2 C1 C2 + sC 2 G1 + G1 G2
(7)
The resonance angular frequency o and quality factor Q are given by o = Fig. 1. The first proposed universal filter.
G1 G2 , C1 C 2
Q=
C1 G 2 . C2 G 1
(8)
322
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
Depending on the voltage status of Vi1 , Vi2 , and Vi3 in the numerator of Eq. (14), one of the following five filter functions is realized: (i) (ii) (iii) (iv) (v)
LP: Vi1 = Vi3 = 0, and Vi2 = Vi , BP: Vi1 = Vi2 = 0, and Vi3 = Vi , HP: Vi2 = Vi3 = 0, and Vi1 = Vi , BS: Vi3 = 0, and Vi1 = Vi2 = Vi , AP: Vi1 = Vi2 = −Vi3 = Vi .
The resonance angular frequency o and quality factor Q are given by G1 G2 C1 G 1 , Q= . (15) o = C1 C2 C2 G 2 Although an inverting voltage input signal is used for realizing the allpass signal. This disadvantage vanishes if we make the resistor R2 be grounded, the capacitor C2 be floating, and insert the voltage input signal Vi3 into the floating terminal of the capacitor C2 , then
Fig. 3. The third proposed universal filter.
Depending on the voltage status of Vi1 , Vi2 and Vi3 in the numerator of Eq. (7), one of the following five filter functions is realized: (i) (ii) (iii) (iv) (v)
LP: Vi1 = Vi2 = 0, and Vi3 = Vi , BP: Vi1 = Vi3 = 0, and Vi2 = Vi , HP: Vi2 = Vi3 = 0, and Vi1 = Vi , BS: Vi2 = 0, and Vi1 = Vi3 = Vi , AP: Vi1 = Vi2 = Vi3 = Vi .
Vo3 =
s 2 C1 C2 Vi1 − sC 2 G2 Vi3 + G1 G2 Vi2 . s 2 C1 C2 + sC 2 G2 + G1 G2
(16)
The AP signal can be obtained from the output terminal Vo3 provided Vi1 = Vi2 = Vi3 = Vi . Note that no inverting amplifiers are needed to construct an AP biquad.
3. Conclusion
The third proposed circuit can be used as either a threeinput single-output or a two-input five-output universal filter is shown in Fig. 3. Circuit analysis yields the following transfer functions: If Vi1 = Vi2 = Vi , and Vi3 = 0, then
Three new voltage-mode universal biquadratic filters are proposed. The first proposed circuit utilized the voltage addition and subtraction characteristics of an FDCCII, which could realize voltage-mode universal biquad filter with arithmetic operations. The second proposed circuit did not need to employ inverting type input signal to realize the five standard filter functions. Moreover, both two universal biquad filters still had the following four main advantages: use of all grounded capacitors and resistors, high-input impedance, no need of matching constraints and no need inverting-type voltage input signals. The third proposed circuit with minimum active and passive components and can be used as either a three-input single-output or a two-input five-output universal filter, which cannot be enjoyed by the previously reported works [5–20].
−G1 G2 Vo1 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(9)
Vo2 s 2 C1 C2 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(10)
Vo3 s 2 C1 C2 + G 1 G 2 = 2 , s C1 C2 + sC 2 G2 + G1 G2 Vi
(11)
Vo4 sC 2 G2 = 2 , Vi s C1 C2 + sC 2 G2 + G1 G2
(12)
Acknowledgement
Vo5 Vo3 − Vo4 s 2 C1 C2 − sC 2 G2 + G1 G2 = = 2 . Vi Vi s C1 C2 + sC 2 G2 + G1 G2
(13)
The author is thankful to the anonymous reviewers for useful suggestions on the earlier version of this paper that improved the paper quality.
On the other hand, the output terminal Vo3 transfer function can be expressed as Vo3 =
s 2 C1 C2 Vi1 + G1 G2 Vi2 + sC 2 G2 Vi3 . s 2 C1 C2 + sC 2 G2 + G1 G2
(14)
References [1] Liu SI, Tsao HW. The single CCII biquads with high-input impedance. IEEE Trans Circuit Syst 1991;38:456–61.
H.-P. Chen / Int. J. Electron. Commun. (AEÜ) 62 (2008) 320 – 323
[2] Fabre A, Dayoub F, Duruisseau L, Lamoun M. High input impedance insensitive second-order filters implemented from current conveyors. IEEE Trans Circuits and Systems – I: Fundam Theory Appl 1994;41:918–21. [3] Chang CM, Al-Hashimi BM, Chen HP, Tu SH, Wan JA. Current mode single resistance controlled oscillators using only grounded passive components. Electron Lett 2002;38:1071–2. [4] El-Adawy AA, Soliman AM, Elwan HO. A novel fully differential current conveyor and applications for analog VLSI. IEEE Trans Circuits and Systems – II: Analog Digital Signal Process 2000;47:306–13. [5] Soliman AM. Kerwin–Huelsman–Newcomb circuit using current conveyors. Electron Lett 1994;30:2019–20. [6] Senani R, Singh VK. KHN-equivalent biquad using current conveyors. Electron Lett 1995;31:626–8. [7] Horng JW, Lay JR, Chang CW, Lee MH. High input impedance voltage-mode multifunction filters using plus-type CCII’s. Electron Lett 1997;33:472–3. [8] Chang CM. Multifunction biquadratic filters using current conveyors. IEEE Trans Circuits and System – II: Analog Digital Signal Process 1997;44:956–8. [9] Chang CM, Lee MJ. Voltage-mode multifunction filter with single input and three outputs using two compound current conveyors. IEEE Trans Circuits and Systems – I: Fundam Theory Appl 1999;46:1364–5. [10] Horng JW, Chiu WE, Wei HY. Voltage-mode highpass, bandpass and lowpass filters using two DDCCs. Int J Electron 2004;91:461–4. [11] Horng JW, Hou CL, Chang CM, Chung WY, Wei HY. Voltage-mode universal biquadratic filter with one input and five outputs using MOCCIIs. Comput Electr Eng 2005;31: 190–202. [12] Horng JW, Hou CL, Chang CM, Chung WY, Wei HY. Voltagemode universal biquadratic filters with one input and five outputs. Analog Integr Circuits and Signal Process 2006;47: 73–83. [13] Horng JW, Tsai CC, Lee MH. Novel universal voltage-mode biquad filter with three inputs and one output using only two current conveyors. Int J Electron 1996;80:543–6.
323
[14] Liu SI, Lee JL. Voltage-mode universal filters using two current conveyors. Int J Electron 1997;82:145–9. [15] Chang CM, Tu SH. Universal voltage-mode filter with four inputs and one output using two CCII + s. Int J Electron 1999;86:305–9. [16] Horng JW. High-input impedance voltage-mode universal biquadratic filter using three plus-type CCIIs. IEEE Trans Circuits and Systems – II: Analog Digital Signal Process 2001;48:996–7. [17] Chang CM, Chen HP. Universal capacitor-grounded voltagemode filter with three inputs and a single output. Int J Electron 2003;90:401–6. [18] Horng JW. High input impedance voltage-mode universal biquadratic filters with three inputs using three plus-type CCIIs. Int J Electron 2004;91:465–75. [19] Chang CM, Al-Hashimi BM, Wang CL, Hung CW. Single fully differential current conveyor biquad filters. IEE Proc Circuits Dev Syst 2003;150:394–8. [20] Chang CM, Chen HP. Single FDCCII-based tunable universal voltage-mode filter. Circuit Syst Signal Process 2005;24: 221–7. Hua-Pin Chen was born in Taipei, Taiwan, Republic of China, in 1966. He received the M.S. and Ph.D. degrees from Chung Yuan Christian University, Chung, Taiwan, in 2001 and 2005, respectively. Since August 2005, he is affiliated as Assistant Professor in the Department of Electronic Engineering at the De-Lin Institute of Technology, Taiwan. His teaching and research interests are in the areas of Circuits and Systems, Analog and Digital Electronics, Active Filter Design, and Current-Mode Signal Processing.